Extrusion coating is a process commonly used to produce composites for use in a wide variety of applications, such as food or medical packaging, document protection, and so forth. Thermal lamination sleeves, for instance, have been formed by melt-extruding a film of an ethylene vinyl acetate copolymer onto a polyester film substrate. One parameter that can have a tremendous impact on the quality of the resulting composite is the ability of the melt-extruded film to adequately adhere to the substrate. For this reason, a variety of techniques have been employed to help improve adhesion. One such technique is to partially oxidize the coating by controlling certain process parameters, including increasing processing temperatures, extending the distance between the die and the substrate (thus increasing the amount of time the hot curtain is in contact with air), or slowing down the line. While these tools may be of some benefit, they all have practical limits. For example, ethylene vinyl acetate copolymers can decompose at high temperatures, which may limit the extent to which processing temperatures can be increased. Increasing the distance between the die gap may likewise lead to an increased transverse direction necking, which limits the width of film that can be coated and increases material waste.
As such, a need currently exists for an improved technique of extrusion coating a film onto a substrate, as well as improved compositions for such processes.